One of the common issues with church acoustics is the need to isolate the sound generated in the sanctuary from adjacent spaces. Often, the sanctuary is part of a larger building, which may house a nursery, meeting rooms and offices. “Isolation is expensive, and there aren’t that many magic bullets to be had in this area,” says John Storyk, founding partner of Highland, N.Y.-based design firm Walters Storyk Design Group (WSDG). Storyk points out that it is much easier to handle the issue up front by taking a realistic look early in the design process at what the sound levels will be in the sanctuary and what the sound levels need to be in adjacent areas.

“Often just re-arranging a space can save construction costs,” Storyk says. “Acoustic isolation design is very difficult to correct after the fact and is also difficult to monitor during construction.”

The goal in sound isolation is to prevent or reduce the sound vibrations from traveling through walls into other rooms, which is commonly measured by a scale called Sound Transmission Class, or STC. In general, the higher the STC rating, the lower the sound transmission.

There are several commonly used methods to reduce sanctuary sound from filling nearby rooms, including:

Double walls: Since the sound needs to vibrate the wall itself to transmit sound to the next room, doubling the wall mass, perhaps with two sheets of drywall instead of one, will reduce the traveling sound as well.

Dampening materials and insulation: Acoustic panels are meant to absorb sound and are often added to assist in channeling sound within a sanctuary. They also limit the amount of sound vibrations that can travel beyond the room. Also, adding loosely packed insulation between walls helps to reduce sound vibrations as well. Material can include standard insulation materials like fiberglass or recycled cotton.

Staggered studs: When two walls share a common stud structure, the studs themselves become excellent sound conductors. By using two sets of non-aligned studs, one for the wall in each room, sound from one room will not travel as well to the other.

Other types of decoupling include resilient clips, which effectively decouple the drywall from the frame in such a way that it reduces its ability to transmit sound vibrations.

How do sound engineers use these techniques?

“We are great fans of panel (membrane) absorbers, since they can be relatively thick and relatively affordable,” says Storyk of WSGD. “There are some pre-fab products on the market, but for larger space (most churches), we usually will end up designing them and having them fabricated, much more economically.”

Scott R. Riedel of Milwaukee-based Scott R. Riedel & Associates turned to a specific product when he needed to isolate sanctuary sound from the rooms below. At St. Mark’s Lutheran Church in Marion, Iowa, Riedel used Kinetics ISO-Max, which involves a series of absorbers, barriers, and resiliently mounted elements, for the sanctuary flooring.

The church had a Sunday-school education room and the organ blower/motor room beneath the sanctuary, requiring a dedicated effort to ensure that sound remained isolated. In addition to the ISO-Max installation, the windows were insulated and the doors were sealed with perimeter gaskets. To keep the organ machinery from filtering into the sanctuary, the air intake was lined with insulation and contained two 90-degree turns to prevent blower noise from exiting through the air-intake.It is also possible to use motorized walls, says Nick Colleran of Acoustics First Corp. in Richmond, Va. “You can do acoustics that change but you need a good budget and a reason for it,” such as a sanctuary that needs to accommodate both a praise band with shorter reverb time and a traditional choir and organ.